This disclosure relates generally to hydrocarbon exploration and production, and in particular, to forming and managing wellbore tubulars or casings to facilitate hydrocarbon exploration and production.
During hydrocarbon exploration, a wellbore typically traverses a number of zones within a subterranean formation. Wellbore tubing strings or casings are then formed in the wellbore. Openings called windows are also formed in the tubing strings or casings for lateral or horizontal hole operations. The main borehole may then be provided with one or more lateral boreholes which branch from the main borehole and extend into one or more wells laterally displaced therefrom. The window may be formed with a whipstock assembly which is located at the required depth and orientated appropriately so as to laterally deflect a milling tool from the main borehole into the surrounding formation. Alternatively, pre-cut or pre-formed windows can also be used.
In many circumstances a main borehole is known to be provided with a window and a lateral borehole, but the precise depth and orientation of the window is unclear. Proper positioning of downhole equipment (such as a deflector or cleanout assembly) relative to the window is difficult to achieve. Consequential delays in running equipment into a lateral borehole can be highly inconvenient and extremely expensive. Thus, when tripping an apparatus into a lined wellbore with a window cut therein, it is sometimes necessary to locate or find the window. For example, coal bed methane (CBM) lateral wells require periodic reentry to remove accumulated debris from the producing horizontal section. The typical operation includes use of a jetting assembly run on coiled tubing to washout coal fines that have collected inside the slotted liner. One aspect of such an operation may be to locate an existing casing window, position a deflector opposite the window and secure the apparatus in place to enable a washing jet assembly to be guided into the lateral hole. Many other applications for apparatus to be located and secured next to a window also exist.
The principles of the present disclosure are directed to overcoming one or more of the limitations of the existing apparatus and processes for locating a downhole window or other opening in a lined borehole.